The present invention relates in general to a mooring buoy which is particularly designed to dive through large, steep swells or waves, including those which may break upon impact with the buoy.
Catenary Anchor Leg Mooring (CALM) buoys are often employed as offshore loading facilities for transferring oil from an onshore or offshore location to an oil tanker, or from an oil tanker to a reception facility. These types of buoys are so named because they employ a plurality of catenary anchor chains to hold the buoy generally in place. An advantage of these buoys is that they do not require construction of a costly jetty or dock for mooring the oil tankers. However, since offshore loading facilities are often located in unprotected waters, the buoys must be designed to accommodate and withstand great environmental forces produced by large swells or waves, high winds and/or strong currents. These environmental forces can become particularly fierce when the buoy is placed in a very shallow location because the waves tend to build up and become very steep before they break in the shallow water.
Typically, the previous CALM buoys have been made with a rectangular vertical cross-section which has a relatively high drag resistance. In addition, the buoys have been made so that they will attempt to climb over the waves as the waves pass by. As a result, very large forces are imposed both on the buoy and the anchor chains holding the buoy. In the past, this problem has been either avoided by moving the buoy further offshore in order to avoid the steep breaking waves, or accommodated by increasing the chain diameter in order to withstand the high forces. Most often, the final design and placement of the buoy represents a compromise between moving the buoy further offshore and increasing the diameter of the anchor chains. Unfortunately, both of these solutions increase the cost of the offshore loading facility considerably.